Information Assurance

4.4. Transport Network Recovery Techniques

We now discuss some of the more common basic methods for performing traffic recovery after a failure.

4.4.1. Automatic Protection Switching

One particular survivability method that can be thought of strictly as a protection mechanism is 1 + 1 automatic protection switching (1 + 1 APS) [12]. In 1 + 1 APS, a primary end-to-end working channel is duplicated via head-end bridging on a dedicated physically diverse backup channel and both channels are monitored by the receiver. Upon failure of equipment along the path of the primary channel (or simple degradation of its signal), the receiver performs a tail-end transfer to select the backup channel. This is the only widely used survivability mechanism where ...